Biology subjects

van den Burg, M. P.

Publications and source records attributed to van den Burg, M. P..

8 recordsLinked to original sources

bioRxiv2026

Reassessing display behavior from Bels et al. (2025) given the complexity of anthropogenic hybridization and intraspecific diversity in Iguana iguana

Understanding behavioral differences between non-native and closely related endangered species could be important to aid conservation management. In volume 169 of Zoology, Bels et al. (2025) reported on their comparison of display-action-patterns (DAP) between native Iguana delicatissima and non-native iguanas present on islands of the Guadeloupe Archipelago in the Caribbean Lesser Antilles. Here, we address conceptual and methodological concerns about their work and reanalyze their data given our proposed corrections, primarily a literature-informed adjustment of their "species" category. We additionally utilize online videos from South American mainland I. iguana populations, from where the non-native iguanas in the Guadeloupe Archipelago originate, to better understand the different DAPs between native and non-native iguanas in the Guadeloupe Archipelago. Significant differences in DAP characteristics among "species" categories (native I. delicatissima, non-native iguanas, and hybrids) show that Bels et al. (2025) oversimplified their data analyses by merging all non-native populations into one group. This result indicates the presence of behavioral variation among subpopulations within widely hybridizing iguanid populations, which has been poorly studied. Additionally, videos from mainland populations across two major mitochondrial clades of Iguana iguana show that non-native iguanas on Guadeloupe retained DAP characteristics of those populations from which they originate. We discuss these findings in light of the proposed hypotheses put forward by Bels et al. (2025), of which two can be excluded. Overall, our reanalysis shows that studies focusing on characteristics within settings of complex hybridization in diverse species should acknowledge this complexity.

zoology↗

bioRxiv2025

Larger hybrid clutch size could drive regional displacement of native Iguana populations across the Lesser Antilles

Native Iguana populations across the Caribbean Lesser Antilles are being replaced by non-native green iguanas (NNGI) once these establish themselves, leading to eventual extinction. Despite this knowledge, and much effort towards NNGI removal and prevention of incursions, the underlying mechanisms of the observed genetic swamping are poorly understood. Previous studies show that larger clutch size is a key reproductive trait of mainland as opposed to insular lizard populations. Higher clutch size in NNGI and their progeny could be a driver in the genetic swamping of insular Iguana populations. We collected data on snout-vent length, tail length, clutch size and genetics opportunistically during an eradication program of hybrid and NNGIs on the island of Saba, home to a native Iguana Iguana population. Data of native and hybrid iguanas from Saba were combined with similar published data from native insular and mainland Iguana populations. Generalized linear modeling revealed that climatic variables could not explain differences in clutch size, in contrast to genetic origins. Our preliminary results show that hybrid iguanas lay significantly more eggs (~40%) than similar-sized native Saba iguanas. Therefore, we suggest that higher hybrid clutch size may be a contributing factor hastening the genetic swamping and declines in native Iguana populations across the Lesser Antilles. Further study is needed to clarify and better understand the drivers of the rapid genetic swamping and loss of Antillean iguana diversity, which should also focus on Iguana delicatissima and utilize genomic approaches to pinpoint genes under selection.

ecology↗

bioRxiv2025

A genomic perspective on the origins, evolution and adaptation of Galapagos iguanas

Island taxa provide opportunities to explore the genomic basis of species diversification and trait evolution arising from adaptation to new environmental conditions and ecological niches. Here we generate the first genomic sequences for the four endemic Galapagos iguana species to reconstruct their evolutionary history and to identify genes which may contribute to their unique adaptations. We show that the marine (Amblyrhynchus) and land (Conolophus) lineages evolved in situ on now submerged islands, following a single colonisation event 9 - 12.4 million years ago. Genomic selection scans identified genes linked to traits potentially facilitating adaptation to the Galapagos environment, including specialised pigmentation phenotypes (e.g. ASIP, BCO2 and KITLG), DNA damage and UV irradiation inflammation responses (e.g. MAPK14 and BRAF), which may contribute to increased resilience to elevated UV exposure at equatorial latitudes. A shift from eumelanin (dark) to pheomelanin (yellow-orange) dominated colouration in Conolophus species may be attributable to fixed substitutions in the MC1R gene that influence protein structure and interactions, with the depigmented skin phenotype of the pink iguana additionally linked to positive selection in regulators of MITF activity, melanosome transport and dermal vasculature unique to that lineage. Further genes with signatures of positive selection in marine iguanas have putative functions including hypoxia response, that may be associated with their transition to underwater foraging (e.g. HBA, HMOX2, HIF), as well as their unique ability to repeatedly shrink and grow in body size through tissue and bone remodelling (e.g. AREG, BMP2, CPNE7). Genome-wide patterns of genetic diversity indicate recent inbreeding coincident with the timing of human settlement. Our study provides insights into the origins and diversification of the iguanas and the molecular basis of adaptation to life in the Galapagos, facilitating future conservation genomic management of threatened iguanid populations.

evolutionary biology↗

bioRxiv2024

Morphometrics as a conservation tool for rapid in-situ distinction of native and introduced iguanas: comparing Iguana delicatissima and Iguana iguana

Invasive alien species severely impact native and endemic species, disproportionately affecting insular species, and this is especially true for Caribbean reptiles. The Lesser Antillean iguana (Iguana delicatissima) experienced a drastic range decline strongly driven by hybridization with non-native green iguanas (NNGI, Iguana iguana species complex). With numerous NNGI populations within the Lesser Antilles, it is a matter of time before these arrive on the last I. delicatisisma inhabited islands, whereupon rapid in-situ identification of non-native and hybrid animals is essential. However, only a few scale and coloration characters allow in-situ identification of NNGI, which are compromised by introgression. Here we assessed the differentiating power of an additional 20 scale and length-dependent characteristics between the I. delicatissima population on St. Eustatius and the established NNGI population on St. Maarten, the main source of arriving stowaway iguanas on St. Eustatius. We identified 14 length-dependent characteristics that significantly differ between I. delicatissima and NNGIs, with multi-variate analysis showing clear morphospace separation and high assignment accuracy of predictive models (>91%). Additionally, the number of femorals and supra digital scales significantly differs between these iguanas. Morphospace knowledge of St. Eustatius I. delicatissima now allows rapid identification of any divergent iguanas using easy to obtain measurements and meristics. Given intraspecific variation in I. delicatissima and green iguanas, we recommend that these characteristics are assessed and validated for other populations, including hybrid individuals. Our work demonstrates the urgent need to invest in baseline morphometric datasets to aid rapid in-situ conservation efforts once NNGI arrive and start to hybridize with I. delicatissima.

zoology↗

bioRxiv2022

Population estimate, natural history and conservation of the melanistic Iguana iguana population on Saba, Caribbean Netherlands

Intraspecific diversity is among the most important biological variables, although still poorly understood for most species. Iguana iguana is a Neotropical lizard known from Central and South America, including from numerous Caribbean islands. Despite the presence of native melanistic I. iguana populations in the Lesser Antilles, these have received surprisingly little research attention. Here we assessed population size, distribution, degree of melanism, and additional morphological and natural history characteristics for the melanistic iguanas of Saba, Caribbean Netherlands based on a one-month fieldwork visit. Using Distance sampling from a 38-transect dataset we estimate the population size at 8233 {+/-}2205 iguanas. Iguanas mainly occurred on the southern and eastern sides of the island, between 180-390 m (max altitude 530 m), with highest densities both in residential and certain natural areas. Historically, iguanas were relatively more common at higher altitudes, probably due to more extensive forest clearing for agricultural reasons. No relationship was found between the degree of melanism and elevation, and few animals were completely melanistic. Furthermore, we found that body-ratio data collection through photographs is biased and requires physical measuring instead. Although the population size appears larger than previously surmised, the limited nesting sites and extremely low presence of juvenile and hatchling iguanas (2.4%), is similarly worrying as the situation for I. delicatissima on neighboring St. Eustatius. The islands feral cat and large goat population are suspected to impact nest site quality, nest success, and hatchling survival. These aspects require urgent future research to guide necessary conservation management.

ecology↗

bioRxiv2021

Hurricane-induced population decrease in a Critically Endangered long-lived reptile

Catastrophic events, like hurricanes, bring lethal conditions that can have population-altering effects. The threatened Caribbean dry forest occurs in a region known for its high-intensity hurricane seasons and high species endemism, highlighting the necessity to better understand hurricane impacts as fragmentation and clearing of natural habitat continues. However, such studies remain rare, and for reptiles are mostly restricted to Anolis. Here we used single-season occupancy modeling to infer the impact of the intense 2017 Atlantic hurricane season on the critically endangered Lesser Antillean Iguana, Iguana delicatissima. We surveyed 30 transects across eight habitats on St. Eustatius during 2017-2019, which resulted in 344 individual surveys and 98 iguana observations. Analyses of abundance and site occupancy indicated both measures for 2018 and 2019 were strongly reduced compared to the pre-hurricane 2017 state. Iguanas at higher elevations were affected more profoundly, likely due to higher wind speeds, tree damage and extensive defoliation. Overall, our results indicate a decrease in population estimates (23.3-26.5%) and abundance (22-23.8%) for 2018 and 2019, and a 75% reduction in the number of opportunistic sightings of tagged iguanas between 2017-2018. As only small and isolated I. delicatissima populations remain, our study further demonstrates their vulnerability to stochastic events. Considering the frequency and intensity of hurricanes are projected to increase, our results stress the urgent need for population-increasing conservation actions in order to secure the long-term survival of I. delicatissima throughout its range.

ecology↗

bioRxiv2020

Illegal trade of morphological distinct population prior to taxonomic assessment and elevation, with recommendations for future prevention

The negative impacts of international wildlife trafficking are well known, and such negative impacts can be even more pronounced for insular species. This dynamic market needs close monitoring, and when novel species appear in the commercial trade relevant authorities should be able to react in order to reduce negative impacts on wild populations. Here we describe a novel case where an insular endemic form of the Iguana iguana complex has entered the international commercial trade, likely stimulated by efforts to elevate the form taxonomically. Despite the absence of authorized export permits from the relevant CITES authority, we identify animals that are sold in a range of countries and the likely pathway and methods of importation. We provide recommendations to prevent future illegal collection and trafficking that could be implemented for other taxa. We call for increased awareness of the higher economic value of taxa considered for future taxonomic elevation, and increased monitoring of the commercial trade in order to act promptly when illegal activity is detected.

ecology↗

bioRxiv2020

The march of the Common Green Iguana (Iguana iguana): early establishment in Singapore and Thailand is facilitated by the pet trade and recreational parks

The popularity of the Common Green Iguana (Iguana iguana) as a pet has contributed to its global occurrence as an invasive alien species. Early detection and control of invasive alien I. iguana populations is necessary to prevent the need for large and financially demanding eradication actions. Here, we collated information from digital footage and interviews regarding sightings of free roaming I. iguana specimens in Singapore and Thailand, and present evidence of early-stage invasions and establishment. Using species distribution modeling, we find that large parts of Thailand and neighboring countries have suitable habitat, which could facilitate the expansion of these alien populations if left uncontrolled. Additionally, we report singular I. iguana sightings in Hong Kong and Peninsular Malaysia. We call for awareness of alien I. iguana in the Philippines due to the high number of pet iguanas and reported CITES importations as well as the availability of suitable habitat throughout the archipelago. Further, we identify I. iguana presence to be facilitated by the release of pet-traded specimens and uncontrolled exhibition practices in recreational parks. We provide recommendations for implementing monitoring and eradication efforts and strategy recommendations to halt future spread and release.

ecology↗